Validating user input strings in Python

Solution 1:

You are testing if the user input is yes or no. Add a not:

while userInput not in ['yes', 'no']:

Ever so slightly faster and closer to your intent, use a set:

while userInput not in {'yes', 'no'}:

What you used is userInput in ['yes', 'no'], which is True if userInput is either equal to 'yes' or 'no'.

Next, use a boolean to set endProgram:

endProgram = userInput == 'no'

Because you already verified that userInput is either yes or no, there is no need to test for yes or no again to set your flag variable.

Solution 2:

def transaction():

    print("Do the transaction here")



def getuserinput():

    userInput = "";
    print("Start")
    while "no" not in userInput:
        #Prompt for a new transaction
        userInput = input("Would you like to start a new transaction?")
        userInput = userInput.lower()
        if "no" not in userInput and "yes" not in userInput:
            print("yes or no please")
        if "yes" in userInput:
            transaction()
    print("Good bye")

#Main program
getuserinput()